It was discovered that a compromised content process could log in to amalicious Firefox Sync account. An attacker could potentially exploitthis, in combination with another vulnerability, to disable the sandbox.(CVE-2019-9812)

It was discovered that addons.mozilla.org and accounts.firefox.com couldbe loaded in to the same content process. An attacker could potentiallyexploit this, in combination with another vulnerability that allowed across-site scripting (XSS) attack, to modify browser settings.(CVE-2019-11741)

It was discovered that the "Forget about this site" feature in thehistory pane removes HTTP Strict Transport Security (HSTS) settings forsites on the pre-load list. An attacker could potentially exploit thisto bypass the protections offered by HSTS. (CVE-2019-11747)

Update instructions:

The problem can be corrected by updating your system to the followingpackage versions:

Ubuntu 19.04: firefox 69.0+build2-0ubuntu0.19.04.1

Ubuntu 18.04 LTS: firefox 69.0+build2-0ubuntu0.18.04.1

Ubuntu 16.04 LTS: firefox 69.0+build2-0ubuntu0.16.04.4

After a standard system update you need to restart Firefox to makeall the necessary changes.